ON THE LIFE-HISTORY OF THE FOEAMINIFERA. 109 



megalospheric (with a large central chamber), and microspheric 

 (with a small central chamber) respectively. 



What is the relation existing between these two forms of a 

 species ? Do they represent two sexes, or do they belong to 

 different generations ? I believe them to belong to different 

 generations. 



In what follows I have attempted to collect the more im- 

 portant evidence which bears on the life-history, and have 

 given an account of my own observations, which deal mainly 

 with two species : — Polystomella crispa (Linn.), belonging to 

 the Perforate division of the group, and Orhitolites complanata, 

 Lamk., a representative of the Imperforata. 



The evidence will be presented under the following heads: — 



1. Previous contributions to the life-history of the Fora- 

 minifera. 



a. Observations on Reproduction and Dimorphism. 



b. The relation of Orbulina and Globigerina. 



c. Observations on Nuclei. 



2. Observations on : — 



a. Polystomella crispa (Linn.). 



b. Orbitolites complanata, Lamk. 



c. Rotalia beccarii (LiNN.). 



d. Truncatulina, d'Orb. 



e. Calcarina hispida, Brady. 



/. Cycloclypeus Garpenten, Brady. 

 '" 3. Concluding Remarks. 



1. Previous Contributions to the Life-History 



OF THE FoRAMINIFERA. 



(a.) Observations on Reproduction and Dimorphism. 



In the year 1847, Gervais (12) brought before the Academic 



des Sciences, an observation on some Triloculine Miliolidce, which 



he had kept in sea water. Young individuals, consisting of a single 



large chamber, with their shells already formed and capable of 



sending out pseudopodia had appeared, in number about 100, 



grouped about the orifice of a parent shell. He also states that 



VOL. VI. 1^ 



